i watch lost enough to have an idea of what is going on, but I need to know why michael killed analucia. did they explain that?

because he wanted to get them to give him back walt. and they said he had to set henry gale free. so he shot her so he got get him out cuz she was the only one guarding the hatch. then libby walk...

so then analucia i[was]i one of "the others" that kidnapped walt?

Analucia was guarding FHG(fake Henry Gale). So to free FHG and make it look like an escape, Michael killed her, and Libby just happend to walk in, so he bust a cap in her too.